In principle Multi link systems can provide the best comfort and handling. But back in the seventies this system wasn't used on any front suspension. Multi link has the future being used by Audi, BMW,etc. Second best is the double wishbone which can give good comfort and good handling if properly set up. For instance most american cars use it but the geometry often leaves room for improvement. And then there is the MacPherson. Giving good comfort (it allows good wheel travel) and reasonable handling.

If MacPherson isn't the best then why did Rover choose it? First Rover wanted to use a double wishbone setup. However it proved very difficult to find room to place the catalytic converters needed for the American market. This fact and the influence of the bean counters at Rover made that finally the MacPherson setup was chosen.

The macPherson is a very simple system and basically is a coil spring and shock absorber built into the spring leg. The leg pivots on a ball joint on the lower control arm. The lower control arm can be an ordinary A-arm, or a narrow lower control arm (track rod) which locates the lower end of the strut in the traverse direction and a separate member called a radius rod locating the assembly in the longitudinal direction. However on the SD1 the anti-roll bar serves a double function as the longitudinal link taking the drive and brake forces and thereby eliminating the separate radius rod.

Roll centre height The calculation of the roll center height is quite straightforward with the next figure. Run a line perpendicular to the spring axis (line nr. 1) Run a line from the lower control arm of the leg to the opposite side (line nr. 2) Lines 1 and 2 intersect at Y Do the same for the other side and you will find X Draw a line from from Y towards the center of the tyre footprint. Do the same from X to the tyre footprint The roll center is at the intersection of the last two lines.

What do we learn from determining the roll center? Well moving the spring leg more upright without changing the lower control arm brings the roll center lower. A greater inclination rises the roll center. But changing spring leg angle has no big effects on roll center height. Raising or lowering the lower control arm pick up point has far more effect. But this will give extreme positive camber on rebound and gives large track variations. This must be avoided and so the engineers can choose the roll center only within a strict limit with the MacPherson. A high roll center isn't possible with the "Mac" and so an anti-roll bar is standard equipment with the MacPherson to compensate for this. Camber variations can be reduced by making the lower control arm longer. But then the arm often gets in the way with the engine. Also notice that the roll center isn't necessary always in the middle of the car. When for instance the right wheel hits a bump the roll center is slightly offset to the left. The roll center also moves inwards when the car goes through a corner.

MacPherson suspension tends to be very sensible to wheel balance and tyre uniformity. This because the mounting points are so far apart. The wheel forces caused by unbalanced wheels are magnified at the suspension pick-up points due to the "leverage" effects.

An advantage of the "Mac" is the low unsprung weight of this system. The spring leg is heavier than an upper control arm but the upper part with spring and shock absorber is sprung weight. Another advantage is that the shockloads from the suspension can be distributed in a widespread area of the body. This helps in a lighter unitary body.

As you can see.....MacPherson has its Pro's and Con's. It's not bad but not very good either. A good MacPherson is still far better than a mediocre double wishbone set up. And the SD1 setup is a good one. Be assured of that.

Let's compare the SD1 front suspension with it's predecessor the P6. As we all know the P6 lay-out is far more complicated with the horizontal mounted spring mounted against the bulkhead. The P6 however was not the first using this setup. The first to use it was Glas on its Isar T-700. The long lower control arm of the P6 gives only small camber changes. By using a leading upper arm the caster angle also varies on the P6 (Not so with our SD1). To minimise caster variations Rover used a very long upper leading arm. The advantage of this design was a very high roll center of 7 inch above the ground. No anti-roll bars needed here.

As roll was very little due to the high roll center soft springs could be used. And because the setup gave enough room for generous wheel travel the P6's ride was very smooth. The unsprung weight is comparable with the SD1 (At least for the front suspension.....the rear suspension is another story). To be honest.....The P6 system works better by a good margin. But it required detachable front wings to reach the upper suspension components. This was out of the question for the SD1 (money...money) and so the P6 suspension set up was never carried over to the SD1.

Is there room to improve our suspension?
There is, off course you can try to move the suspension pick up points and optimise them even further for your driving conditions. But that goes a bit to far for the average enthousiast. Here are some other points to consider.

• Go for Vitesse wheels. They look nicer and reduce the unsprung weight.
• Use tyres of a known brand (Michelin tends to work good for our car but expensive!).
• Carefully balance the wheels....the Mac is sensitive to it as you know by now.
• Koni's have proven to be the best shockers for the SD1. Better than Monroe or Spax giving superior damping and long life. Yes, it happens to be a Dutch brand :)
• Use polyurethane suspension bushes. They provide better horizontal location of the suspension and give better feel in the steering. They also last longer than the rubber onces which should be replaced every 5 years. The polyurethane bushes do stiffen things up and make the ride a little harsher though.
• Better roadholding without stiffer/lower springs?....use a heavier anti-roll bar at the front. It makes the car more stable (more understeer) and only stiffens the suspension a bit when one wheel is lifting.

  Thanks to: Adriaan Briene